Method of galvanizing

ABSTRACT

A method of galvanizing batches of articles wherein the articles are placed in a perforate basket which is suspended from a rail above a workpath. The thusly suspended articles are first dunked in pickling, rinsing and fluxing solutions and then into a zinc bath where the basket and articles are spun to remove flux. The basket is then removed from the bath, moved directly to a position over a quench tank and again spun so that spelter falls into the tank for removal as shot. The basket and articles are also spun while being lowered into the quench tank; after the quenching step; and during certain of the other above described steps so as to result in varying degrees of product improvement.

United States Patent 1191 Garrison Aug. 21, 1973 METHOD OF GALVANIZING1,119,934 10/1930 Giblin 111/101 Inventor: William HGl I RichmondVa'2,273,250 2/1942 Charlton 117/101 F El N ATEN S PPL AT NS [73] AsslgneezAmerican Spln-A-Batch Company, 1 3 3 5 G T IC I0 118 54 Richmond Va reatrttam [221 Filed 1972 im??? smi" '#R Rh..$-, 111 1 211 App] N 255 0AJtqmey-B. Franklin Grifiin, Alan E. J. Branigan e a Related US.Application Data [63] Continuation of Ser. No. 111, Jan. 5, 1910, [57]AESTRACT abandoned A method of galvanizing batches of articles whereinthe articles are placed in a perforate basket which is sus- [52] Cl117/51 1 5 pended from a rail above a workpath. The thusly sus- 51 I tCl 3 pended articles are first dunked in pickling, rinsing and d cfluxing solutions and then into a zinc bath where the l 1 e 71?; C 4 411 basket and articles are spun to remove flux. The basket l 4 is thenremoved from the bath, moved directly to a position over a quench tankand again spun so that spelter [561 References (med falls into the tankfor removal as shot. The basket and UNITED STATES PATENTS articles arealso spun while being lowered into the 1,140,068 5/1915 Roberts 118/54quench tank; 'after the quenching step; and during cerl,252.005 1/1918Hess 117/101 X tain of the other above described steps so as to resultKelley 1. in varying degrees of product i provernent 1,748,363 2/1930Peirce, Jr 118/54 16 Claims, 5 Drawing: Figures SPIN SPIN COAT QUENCHPRE-COATING PAIEmwww ma 3.753762 saw 1 022 FIG.

Hf/Ol? ART l6 [-IZ 14 I87 PICKLE, RINSE a COAT QUENCH FLUX FIG. 2

SPIN SPIN COAT QUENCH PRE-coAT|Ne- FIG. 3

juvsmon WILLIAM H. GARRISON BY .Bram'qan m ATTORNEYS PATENIEmncm um I3.753762 SHEEI 2 OF 2 FIG. 4

mvsmon WILLIAM H. GARRISON y g ffl'mjraniqan MHZ/ Mus ATTORNEYS METHODOF GALVANIZING This is a continuation, division, of application Ser. No.771, filed 5 Jan. 1970, now abandoned.

GALVANIZING METHOD AND APPARATUS Conventional methods of galvanizingbatches of articles usually include a spinning step to throw off surplusmolten zinc or spelter. In this respect, as described in US. Pat. No.1,324,228 to Watrous, after certain surface preparation steps, thearticles to be galvanized are dipped in a kettle or tank of molten zinc.The articles are then removed and usually placed in a floor mountedcentrifuge to remove the spelter which strikes the side of thecentrifuge for subsequent removal. The articles are then removed fromthe centrifuge while they are still hot, and dipped in a quench tank.The thusly coated articles are then removed from the quench tank.

There are many drawbacks to the above described conventional galvanizingprocess, but it has been used for years with only minor modificationsbeing made from time to time. One of the major drawbacks of theconventional process has been the need for transferring the coatedarticles to the centrifuge. This has been required, however, becausesuch centrifuges are large and highly specialized pieces of equipmentwhich, for purposes of stability, must be securely mounted to the floor.Hence, it is an object of this invention to provide a method which doesnot require the coated articles to be transferred to a centrifuge.

In addition, as a practical matter, conventional centrifuging methodsare limited to use in connection with the coating of relatively smallarticles having a maximum length of about 24 inches or so because thecost of larger centrifuges is almost prohibitive. Consequently, it isanother object of the invention to provide a more practical andeconomical method and apparatus for galvanizing articles which range insize from about a half-inch all the way up to about 48 inches in lengthor larger. In this respect, it has been quite difficult tosatisfactorily galvanize large batches of small articles such as woodscrews, for example. Among other reasons, this is because the flux inthe zinc bath has a tendency to lodge in the recesses of the coatedarticles. In the case of batch dipped wood screws, for example, theslots in the head become clogged and the thusly coated threads are oftentoo shallow. This not only produces an inferior product, but also wasteszinc. Other objects of the invention, therefore, are to provide agalvanizing method which uses less zinc and produces a higher qualitygalvanized product. In this respect, it should be noted that theinvention not only provides a more economical method, but also producesa superior quality galvanized product having a wider range of sizes thanthose of the prior art. It should be similarly noted that inconventional galvanizing methods some of the excess zinc appears asspurs" on the surfaces of the galvanized articles. But my methodsubstantially eliminates those spurs so as to result in much saferproduct.

Articles galvanized by conventional centrifugal methods have also beenplagued with water staining or white rust which occurs after thequenching step. Hence, it is another object of this invention to producea high quality galvanized articles that is free of water stains.

Finally, it is an object of the invention to provide a simple, easilymaintainable apparatus for practicing the method of the invention so asto produce higher quality galvanized articles in less time than haspreviously been required.

SUMMARY OF THE INVENTION In accordance with the broader aspects of myinventive method, the articles to be galvanized are first placed in aspinable perforate container or basket that is hung so as to be freelysuspended above a workpath comprised of a series of vats or tanks usedduring the process. The basket and its contents are first sequentiallydipped in suitable pre-coating tanks containing pickling, rinsing, andflux solutions. The'basket and its thusly prepared articles are thendipped into a molten zinc bath where they are galvanized. While the articles are still suspended in the galvanizing basket, they are next movedover the quench tank where the basket and articles are spun whilesuspended above the quench tank to remove the excess molten zinc orspelter which drops into the quench tank for subsequent removal in theform of shot. Next, while still spinning, the basket and articles arelowered into the quench tank for quenching. This is followed by removaland drying. Significantly, the thusly galvanized articles are suspendedduring the entire process of the invention. Hence, it is not necessaryto perform the previously required steps of transferring the articlesinto a separate centrifuge or again transferring them back to the quenchtank after they are spun.

In addition, the apparatus of my invention permits the articles to bespun during any of the above noted process steps. In this respect, Ihave found that the pickling process is both faster and more adequatewhen the basket and articles are spun while they are in the picklingtanks. They can also be spun dry after pickling so as to obtain thebenefits of such a drying step without applying heat as has beenrequired in the past. Similarly, when they are spun while in the zincbath, flux is more completely and uniformly removed which, as notedabove, results in a superior product, particularly for small articlessuch as wood screws which have many relatively small recesses anddepressions where flux tends to lodge. Also similarly, objectionablezinc spurs are substantially eliminated when the basket and parts arespun as they are dunked in the quench tank; the coating has a moreuniform hardness when the basket is spun during the quench step; andwhen a spinning step is added after quenching the resulting product issubstantially free from white rus or water staining. Consequently, itwill be appreciated by those skilled in the art that my apparatus notonly results in an economical process, but provides a product that issuperior to that of the prior art.

Insofar as the apparatus aspects of my invention are concerned, a meansis provided for moving the suspended perforate basket horizontally abovethe various tanks and selectively raising and lowering the basketvertically to dunk the articles. A means is also provided forselectively spinning the basket at controlled speeds so that the methodof the invention can be practiced as described above.

U.S. Pat. No. 3,310,027 to Lindemann is pertinent to these apparatusaspects of my invention, but the Lindemann structure is not suited forthe practice of my method. Firstly, Lindemann does not describe agalvanizing apparatus and has no structure such as my perforate basketfor spinning large batches of articles. Se-

condly, my structure permits the basket to be spun during any or allparts of its horizontal and vertical travel; whereas Lindemannsapparatus can only spin individual articles at two specific locations;and thirdly, the motion of Lindemanns coated article is confined to afixed closed path, so that it does not have the flexibility required forgalvanizing apparatus which use different sizes and locations of tanksdepending on the type of articles being galvanized.

In addition to fulfilling the above objects, my invention also hascertain other advantages. For example, when the basket is spun in thezinc bath to dislodge undesired flux, the zinc is also more evenlydistributed on each article and the incidence of undesired occlusions isgreatly reduced if not substantially eliminated. Also, when the spelteris spun out of the basket over the quench tank, it falls into the tankso that it can be easily removed as shot and returned to the zinc bath.But when conventional floor mounted centrifuges are employed, thespelter is far more difficult to recover. It should also be noted thatbecause of the short time lag between removal of the basket from thezinc bath and the spin step over the quench tank, my method produces amore uniform coating without the hills and valleys which occur whenfloor mounted centrifuges are employed.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects,features, and advantages of the invention will be apparent from thefollowing more particular description of preferred embodiments of theinvention as is illustrated in the accompanying drawings, whereinreference characters refer to the same parts throughout the differentviews. The drawings are not necessarily drawn to scale. Instead, theyare merely presented so as to illustrate the principles of the inventionin a clear manner.

FIG. 1 is a schematic representation of a prior art process forgalvanizing metal;

FIG. 2 is a schematic representation of the method of the invention;

FIG. 3 is a pictorial representation of certain apparatus of theinvention including control means therefor;

FIG. 4 illustrates an air motor and mechanical coupling (partiallybroken-away) for spinning a suspended perforate galvanizing basket; and,

FIG. 5 is a sectional view taken along the lines 5-5 in FIG. 3.

DETAILED DESCRIPTION As noted above, conventional methods of galvanizingbatches of articles include the steps of dipping the articles in aseries of pre-coating tanks of pickling, rinsing, and fluxing solutions.These tanks are located along a given work path and are schematicallyillustrated in FIG. 1 by a single tank 12. The articles to be coated arethen conventionally placed in a tank such as 14 containing a molten zincbath covered with flux. Next, the flux is swept back and the parts areremoved to be placed in a centrifuge 16 where they are spun toremoveexcess zinc. The parts are then quenched in a suitable quenchingsolution located in tank 18.

In accordance with the method of the instant invention, the parts to becoated are placed in a perforate basket 20 in FIG. 2 which is freelysuspended above the workpath and adapted to undergo horizontal andvertical motion in the direction of the arrows 22 and 24 respectively inother words, the basket is portable along the above the workpath withouta need to remove the articles to be coated. The basket 20 is alsoadapted to be selectively spun as indicated by arrow 26 at controlledspeeds of up to about 725 rpm in a preferred embodiment of theinvention. In this manner, the basket and the parts to be coated can bespun at selected speeds in any of the baskets various positions.

In practicing the method of my invention, the parts to be coated arefirst placed in the suspended basket which is then sequentially dunkedinto the various pickling, rinsing, and fluxing solutions. In thisrespect, I prefer to first dunk in an alkali bath comprised of a causticsoda solution. Next, the articles are rinsed in a water bath beforebeing placed in a sulfuric acid pickling solution and then water rinsedagain. The articles are then dipped in either a muriatic acid fluxsolution or one of the commercial fluxes such as that sold by Du- Pontunder the Trademark ZACLON. It should be noted that at this point I havefound the pickling, rinsing and fluxing steps to be both more rapid andmore adequate when the basket is spun at a speed of up to about rpmwhile it is in the various schematically illustrated tanks 28.

After pickling, the basket is spun until dry and then moved above a tank30 containing the molten zinc bath 32 covered by a flux such as ZALCON.The basket is then lowered into the zinc bath. Next, the zinc baths fluxis skimmed back in a conventional manner and the basket is spun at aspeed of about 100 rpm and preferably about 50 rpm while suspended inthe bath. As this occurs the flux can be observed leaving the coatedarticles and rising to the surface of the otherwise skimmed bath. Thisspinning step is continued until the flux stops rising at which timethere is no longer any appreciable amount of flux lodged in the recessesof the galvanized articles. In this manner, the articles are not onlyfree of flux, but the zinc coating has fewer high spots than in the pastso as to result in a saving of zinc even though the galvanized productis of an overall higher quality.

After coating, the flux is again skimmed from the bath, and the basketis removed to be suspended over a quench tank 34 which is surrounded onat least one side by shields 36 which have been partially broken away inFIG. 2. Once the basket is located above the quench tank 34 it is spunat a relatively high speed such as about 725 rpm in the preferredembodiment noted above. When the basket is spun in this manner, thespelter is spun out of the baskets perforations to either fall into thequench tank 34 or strike the shields 36 which direct the spelter intothe quench tank. In either event, the spelter collects in the bottom ofthe quench tank in the fonn of shot which can be subsequently easilyremoved so that it can be either used to replenish the zinc bath orotherwise reclaimed.

While the basket is still spinning it is next lowered into the quenchingsolution for cooling. Spinning at this time prevents the formation ofspurs. The basket is then removed from the quench tank and air driedwhile it is again spun. In this manner, the familiar water staining orwhite rust is prevented.

From the above discussion, it will be appreciated that the method of theinvention is not only simple, but eliminates the previous requirementfor a separate centrifuge; permits the coated articles to be quenchedwhile they are at a higher temperature to prevent them from stickingtogether, and eliminates the need for separately transferring the coatedarticles into a centrifuge and then out again into a quench tank. Inthis respect, it should be noted that the time between the zinc bath andquench is much less than in conventional methods so as to result in lessbuild up of zinc on parts such as threaded bolts or the like. Inaddition, the method of the invention generally results in a superiorproduct that is evenly coated, bright, and free of both water stainingand flux clogging as well as being substantially spurless.

Having described the method of the invention, the apparatus thereof willnow be described with reference to FIG. 3.

The basket is perforated throughout its surface and has a sturdy eye 38on a handle 40 for accommodating a hook 42 extending out of the bottomof a drive linkage housing 44 of a spin air motor housing 46. The basketalso has a tubular center column 49 (FIG. 5) which extends upwardly toor above the baskets rim. This center column functions to keep thebaskets load more evenly distributed during spinning so as to preventeccentric loads from causing the basket to walk about during the variousspinning steps.

Another eye 48 is affixed to the top of the spin motor housing andreceives a second hook 50 extending from a hoist-pulley assembly 52. Acable 54 extends from a drum (not shown) on a reversible drive air motor56 under control of a vertical control throttle valve 58 which isconnected to the vertical drive motor 56 by means of an air supply tube60. The other end of the cable 54 is affixed to a point not shown on asecond reversible-drive air motor assembly 62. In this respect, both ofthe drive motors 56 and 62 are mounted on a horizontal rail 64corresponding to the arrow 22 in FIG. 2. Consequently, as air power isdirected to drive motor 62 by means of a horizontal drive motor throttlecontrol 66 and a second air supply tube 68, the two drive motors and aconnecting arm 70 are selectively moved back and forth across the rail64. In this manner, the basket 20 is suspended above the work bath forselective motion to its various process positions in the mannerdescribed in connection with the inventions method.

The spin motor located in the spin motor housing 46 receives airpressure from a pipe 72, see sketch FIG. 3, through a spin controlthrottle 76. In this respect, as is illustrated in more detail in FIG.4, the spin air motor is rigidly affixed within the housing 46 by bolts47 and has a square ended output shaft 78 which, under control ofthrottle 76, spins freely within a support tube 80 having flanges 82 and84 on either end thereof. The upper flange 82 is bolted to the spinmotor housing 46 as shown in FIG. 4 and the flange 84 is bolted to alower cover member 86, also as shown.

The hook 42 has a square female socket 88 affixed to a collar 90 at theupper end thereof. As illustrated, the female socket 88 engages thesquare output shaft 78 of the spin motor so that rotation of the spinmotor is transmitted to the hook 42 which is supported and journaled forrotation within bearings 92 and 94 which are suitably press flt intoshoulders on the lower cover It should be particularly noted andappreciated that the weight of the basket 20 and its contents istransmitted from the collar 90 on the hook 42 to the upper bearingassembly 92, the lower cover 86, the doubly flanged tube 80 and the spinmotor housing 46 to the upper eye 48. In this manner, none of thebaskets weight is placed on the spin motor so that it is protected andinsured of a longer life.

By virtue of the above described structure, the basket is adapted toundergo selective vertical motion under control of vertical throttlecontrol 58; and selective horizontal motion under control of horizontalthrottle control 66. At the same time the speed at which the basket isspun at any given time is under control of the spin control valve 76.

It is apparent that larger articles to be galvanized require largerbaskets; and in this respect, the invention has been employed withseveral types of baskets. It should be noted however, that it has beenfound more satisfactory to use different perforation sizes and spacingsfor different basket sizes. The following table sets forth some of thedimensional parameters for baskets which have been found to operatesatisfactorily in the practice of the invention. In each case the centercolumn 49 was comprised of a 4 inch diameter pipe.

No. I No. 2 No. 3 No. 4 Diameter, inches 16 22 33 20 Depth, inches 22 3036 48 Metal thickness 3/16" Perforation hole sizes a" #6" 46" $6" HoleSpacing (centers) 56" W 56" As noted above, it has been foundsatisfactory to use a spin motor having a spin speed variation of from 0to about 725 rpm. In some specific applications it might be desirable toemploy a higher speed air motor, but generally speaking 725 rpm is anadequate maximum. One air motor having that speed range consumed air atthe rate of 48 cubic feet per minute at 90 lbs. per square inch inputpressure.

In terms of production capacity, the method and apparatus of theinvention provides startling results. For example, prior art structures,as. a practical matter, have had maximum batch weights of about 250 lbs.per load so as to result in an hourly maximum galvanizing capacity ofabout 3,000 lbs. per hour. When the above described invention isemployed, however, 2,000 lbs. per load can be easily accommodated andthe hourly output capacity is 24,000 lbs. or more. Moreover, and perhapsmost significantly, use of the invention has cut overall productioncosts to less than one third of those of current methods; and laborcosts have been reduced to almost one fourth of those of currentmethods. Consequently, when these startling cost reductions are coupledwith a realization that my invention also results in a superior product,it will be appreciated that the invention has wide application and use.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention. For example, the various pneumatic elements can be replacedby suitable electrical motors and switches. In fact, the rail and motorstructure illustrated in FIG. 3 can be replaced by a vertically moveableswinging boom. Similarly, although the invention has been described interms of manual control by means of above each work station so that thesuspended perforate basket and its contents can be selectivelysequentially moved by a crane or the like from one work station toanother.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A suspended centrifuge method of spin galvanizing articles comprisingthe steps of:

freely suspending said articles from above a workpath so that saidarticles are adapted to be selectively spun about a substantiallyvertical axis at selected locations along the workpath;

lowering said suspended articles into a molten zinc bath to coat saidarticles with zinc;

raising said suspended articles from said zinc bath;

promptly spinning said suspended articles about said vertical axis whilesaid articles remain suspended to remove excess zinc therefrom beforeundesired zinc build-up occurs; and

lowering said suspended articles into a quench tank promptly after saidzinc removal step while said articles are spinning and still at asufficiently high temperature that the articles do not stick together.

2. The method of claim 1 wherein the excess zinc removal spinning stepoccurs while said articles are suspended over said quench tank wherebyspelter is permitted to fall into said quench tank.

3. The method of claim 2 including the step of removing said spelterfrom said quench tank.

4. The method of claim 1 including the step of removing said suspendedarticles from said quench tank; and,

drying said suspended articles by spinning after removal from saidquench tank.

5. The method of claim 1 wherein the step of freely suspending saidarticles includes placing said articles in a spinable perforatecontainer.

6. The method of claim 1 including the step of immersing the suspendedarticles in a pre-coating solution prior to immersion of said articlesin said molten zinc bath.

7. The method of claim 6 including the step of spinning said suspenedarticles while immersed in said precoating solution.

8. The method of claim 6 including the step of spinning said articlesafter removal from said pre-coating solution and prior to immersion insaid molten zinc bath.

9. A suspended centrifuge method of spin galvanizing articles comprisingthe steps of:

freely suspending said articles from above a workpath so that saidarticles are adapted to be selectively spun about a substantiallyvertical axis at selected locations along the workpath;

lowering said suspended articles into a molten zinc bath to coat saidarticles with zinc;

spinning said articles while said articles are immersed in said zincbath so that undesired flux is removed from the surface of said articleswhile said articles are in said zinc bath;

raising said suspended articles from said zinc bath;

promptly spinning said suspended articles about said vertical axis whilesaid articles remain suspended to remove excess zinc therefrom beforeundesired zinc build up occurs; and

lowering said suspended articles into a quench tank promptly after saidzinc removal step while said articles are still at a sufficiently hightemperature that the articles do not stick together.

10. The method of claim 9 wherein said articles are coated with afluxing agent prior to immersion in said molten zinc bath; and saidspinning of said articles while immersed in said zinc bath is terminatedand said articles are raised from said zinc bath when said fluxing agentceases to float to the top of said zinc bath during said spinning insaid zinc bath.

11. The method of claim 9 wherein said articles are spun while beinglowered into said quench tank.

12. The method of claim 9 wherein the excess zinc removal spinning stepoccurs while said articles are suspended over said quench tank wherebyspelter is permitted to fall into said quench tank.

13. The method of claim 12 including the step of removing said spelterfrom said quench tank.

14. The method of claim 9 including the step of removing said suspendedarticles from said quench tank; and,

drying said suspended articles by spinning after removal fromsaid'quench tank.

15. The method of claim 9 wherein the step of freely suspending saidarticles includes placing said articles in a spinable perforatecontainer.

16. The method of claim 9 including the step of spinning said articleswhile said articles are immersed in said quench tank.

2. The method of claim 1 wherein the excess zinc removal spinning stepoccurs while said articles are suspended over said quench tank wherebyspelter is permitted to fall into said quench tank.
 3. The method ofclaim 2 including the step of removing said spelter from said quenchtank.
 4. The method of claim 1 including the step of removing saidsuspended articles from said quench tank; and, drying said suspendedarticles by spinning after removal from said quench tank.
 5. The methodof claim 1 wherein the step of freely suspending said articles includesplacing said articles in a spinable perforate container.
 6. The methodof claim 1 including the step of immersing the suspended articles in apre-coating solution prior to immersion of said articles in said moltenzinc bath.
 7. The method of claim 6 including the step of spinning saidsuspened articles while immersed in said pre-coating solution.
 8. Themethod of claim 6 including the step of spinning said articles afterremoval from said pre-coating solution and prior to immersion in saidmolten zinc bath.
 9. A suspended centrifuge method of spin galvanizingarticles comprising the steps of: freely suspending said articles fromabove a work-path so that said articles are adapted to be selectivelyspun about a substantially vertical axis at selected locations along theworkpath; lowering said suspended articles into a molten zinc bath tocoat said articles with zinc; spinning said articles while said articlesare immersed in said zinc bath so that undesired flux is removed fromthe surface of said articles while said articles are in said zinc bath;raising said suspended articles from said zinc bath; promptly spinningsaid suspended articles about said vertical axis while said articlesremain suspended to remove excess zinc therefrom before undesired zincbuild up occurs; and lowering said suspended articles into a quench tankpromptly after said zinc removal step while said articles are still at asufficiently high temperature that the articles do not stick together.10. The method of claim 9 wherein said articles are coated with afluxing agent prior to immersion in said molten zinc bath; and saidspinning of said articles while immersed in said zinc bath is terminatedand said articles are raised from said zinc bath when said fluxing agentceases to float to the top of said zinc bath during said spinning insaid zinc bath.
 11. The method of claim 9 wherein said articles are spunwhile being lowered into said quench tank.
 12. The method of claim 9wherein the excess zinc removal spinning step occurs while said articlesare suspended over said quench tank whereby spelter is permitted to fallinto said quench tank.
 13. The method of claim 12 including the step ofremoving said spelter from said quench tank.
 14. The method of claim 9including the step of removing said suspended articles from said quenchtank; and, drying said suspended articles by spinning after removal fromsaid quench tank.
 15. The method of claim 9 wherein the step of freelysuspending said articles includes placing said articles in a spinableperforate container.
 16. The method of claim 9 including the step ofspinning said articles while said articles are immersed in said quenchtank.